Atmel AVR10004: RCB256RFR2 – Hardware User Manual [APPLICATION NOTE]
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Figure 4-5. RCB256RFR2 bottom layer design details.
The RCB256RFR2 demonstrates a low-cost two-layer PCB design with a total thickness of 1.6mm. The chosen PCB
material is FR4 (ISOLA IS400). The top and bottom layer each with 35µm copper are used as ground planes.
Performance is achieved without using additional inner ground and supply planes.
Figure 4-6. PCB layer stack.
4.7.2
PCB detail 1 – balanced RF fan out
The radio transceiver RF ports require a small serial inductance in series with the balun or antenna pins. A reasonable
inductance value is 1..2nH. With the g
iven 1.5mm RF4 substrate, it is not possible to design a differential 100Ω
transmission line. Thus, traces between filter-balun and single chip are kept at a reasonable small width of 0.2mm. With
this approach, transmission lines are well routable and create the required inductance at the same time.
